Scroll compressor

ABSTRACT

To suppress reduced rotational moments that occur at a movable scroll. A scroll compressor ( 1 ) includes a fixed scroll ( 2 ), a movable scroll ( 3 ), and an anti-rotation mechanism ( 30 ). A spiral movable wrap ( 3   b ) of the movable scroll ( 3 ) meshes with a spiral fixed wrap ( 2   b ) of the fixed scroll ( 2 ). A first compression chamber (C 1 ) is formed by an inner wall surface ( 3   b   1 ) of the movable wrap ( 3   b ) and an outer wall surface ( 2   b   2 ) of the fixed wrap ( 2   b ). A second compression chamber (C 2 ) is formed by an inner wall surface ( 2   b   1 ) of the fixed wrap ( 2   b ) and an outer wall surface ( 3   b   2 ) of the movable wrap ( 3   b ). After a winding terminal end ( 3   f ) of the movable wrap ( 3   b ) contacts the outer wall surface ( 2   b   2 ) of the fixed wrap ( 2   b ) and the first compression chamber (C 1 ) is thereby closed, a winding terminal end ( 2   f ) of the fixed wrap ( 2   b ) contacts the outer wall surface ( 3   b   2 ) of the movable wrap ( 3   b ) and the second compression chamber (C 2 ) is thereby closed.

TECHNICAL FIELD

The present invention relates to a scroll compressor.

BACKGROUND ART

The scroll compressor disclosed in Patent Document 1 includes a scroll unit including a fixed scroll and a movable scroll, and an anti-rotation mechanism that prevents the rotation of the movable scroll. The fixed and movable scrolls are configured such that a spiral wrap is erected on a bottom plate, and the center of the base plate and the center (spiral center) of the base circle of the wrap are shifted from each other; and a closed space is formed in the scroll unit by meshing the fixed scroll with the movable scroll such that the wraps of the fixed and movable scrolls face each other. The volume of the closed space is changed by revolving the movable scroll around the axial center of the fixed scroll while preventing the rotation of the movable scroll with the anti-rotation mechanism. Patent Document 1 discloses that the anti-rotation mechanism is implemented by a circular hole formed on the back surface of the bottom plate of the movable scroll and a pin that protrudes from a housing wall facing the back surface of the bottom plate of the movable scroll and engages with the circular hole. Also, according to Patent Document 1, a rotational moment occurs in the movable scroll because of a compression reaction force resulting from the compression of the scroll compressor, and a load caused by the rotational moment is applied to the anti-rotation mechanism.

REFERENCE DOCUMENT LIST Patent Document

-   Patent Document 1: JP 2015-059517 A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

The inventors of the present invention have discovered a phenomenon that during the operation of the scroll compressor as described above, the rotational moment momentarily disappears, and as a result, the pin momentarily moves away from the inner surface of the circular hole and then collides again with the inner surface of the circular hole.

An object of the present invention is to suppress reduced rotational moments that occur at the movable scroll.

Means for Solving the Problem

According to first and second aspects of the present invention, a scroll compressor includes a fixed scroll including a fixed bottom plate having a discharge hole in the center of the fixed bottom plate, and a spiral fixed wrap erected on the fixed bottom plate, a movable scroll including a movable bottom plate and a spiral movable wrap that is erected on the movable bottom plate and is meshed with the fixed wrap, a first compression chamber formed by an inner wall surface of the movable wrap and an outer wall surface of the fixed wrap, a second compression chamber formed by an inner wall surface of the fixed wrap and an outer wall surface of the movable wrap, and an anti-rotation mechanism that prevents the rotation of the movable scroll. The scroll compressor is configured such that the movable scroll is caused to revolve around the axial center of the fixed scroll while the rotation of the movable scroll is prevented by the anti-rotation mechanism to change the volume of the first compression chamber and the volume of the second compression chamber and thereby cause a fluid in the first compression chamber and a fluid in the second compression chamber to be compressed separately and then discharged together through the discharge hole into a discharge chamber.

According to the first aspect of the present invention, an involute angle from a reference point on a base circle of the fixed wrap to a winding terminal end of the fixed wrap is less than an involute angle from a reference point on a base circle of the movable wrap to a winding terminal end of the movable wrap.

According to the second aspect of the present invention, after a winding terminal end of the movable wrap contacts the outer wall surface of the fixed wrap and the first compression chamber is thereby closed, a winding terminal end of the fixed wrap contacts the outer wall surface of the movable wrap and the second compression chamber is thereby closed.

Effects of the Invention

According to the first aspect and the second aspect of the present invention, the pressure in the first compression chamber becomes constantly higher than the pressure in the second compression chamber. This makes it possible to constantly generate a rotational moment in the movable scroll and thereby makes it possible to suppress reduced rotational moments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a scroll compressor according to an embodiment of the present invention;

FIG. 2 is a plan view of a fixed scroll;

FIG. 3 is a plan view of a movable scroll;

FIG. 4 is a cross-sectional view taken along line A-A of FIG. 3 ;

FIG. 5 is an enlarged cross-sectional view of one of rotation prevention parts constituting an anti-rotation mechanism;

FIG. 6 is a drawing illustrating a layout of rotation prevention parts of an anti-rotation mechanism on a movable bottom plate;

FIG. 7 is a drawing illustrating an operating state of the scroll compressor;

FIG. 8 is a drawing illustrating an operating state of the scroll compressor;

FIG. 9 is a drawing illustrating an operating state of the scroll compressor;

FIG. 10 is a drawing illustrating an operating state of the scroll compressor;

FIG. 11 is a drawing illustrating an operating state of the scroll compressor;

FIG. 12 is a graph showing relationships between pressures in compression chambers and a crank angle; and

FIG. 13 is a graph showing a relationship between a force (rotational moment) applied to a pin and a crank angle.

MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention is described below with reference to the accompanying drawings.

FIGS. 1 to 6 illustrate a configuration of a scroll compressor according to an embodiment of the present invention. FIG. 1 is a cross-sectional view illustrating an overall configuration of the scroll compressor. FIG. 2 is a plan view of a fixed scroll. FIG. 3 is a plan view of a movable scroll. FIG. 4 is a cross-sectional view taken along line A-A of FIG. 3 . FIG. 5 is an enlarged cross-sectional view of one of rotation prevention parts constituting an anti-rotation mechanism. FIG. 6 is a drawing illustrating a layout of the rotation prevention parts of the anti-rotation mechanism on a movable bottom plate.

A scroll compressor 1 includes a scroll unit 4 including a fixed scroll 2 and a movable scroll (orbiting scroll) 3 that are disposed to face each other in a central axis direction. As illustrated in FIG. 2 , the fixed scroll 2 includes a spiral fixed wrap 2 b that is integrally erected on a fixed bottom plate 2 a. Similarly, as illustrated in FIG. 3 , the movable scroll 3 includes a spiral movable wrap (orbiting wrap) 3 b that is integrally erected on a movable bottom plate (orbiting bottom plate) 3 a.

As illustrated in FIGS. 2 and 3 , the fixed wrap 2 b and the movable wrap 3 b are formed, respectively, along involute curves (virtual lines) that extend from base circles (virtual circles) 2 c and 3 c. Here, an involute angle θ1 illustrated in FIG. 2 indicates an angle that is around a center (fixed spiral center) 2 d of the base circle 2 c and from a reference point (the start point of the involute curve) 2 e on the base circle 2 c to a winding terminal end 2 f of the fixed wrap 2 b. An involute angle θ2 illustrated in FIG. 3 is an angle that is around a center (movable spiral center) 3 d of the base circle 3 c and from a reference point (the start point of the involute curve) 3 e on the base circle 3 c to a winding terminal end 3 f of the movable wrap 3 b.

The involute angle θ1 is less than the involute angle θ2. In the present embodiment, the involute angle θ1 is 820 degrees, and the involute angle θ2 is 850 degrees. However, the involute angles θ1 and θ2 are not limited to these values. Increasing the difference between the involute angle θ2 and the involute angle θ1 increases the pressure difference between a first compression chamber C1 and a second compression chamber C2 described later and makes it possible to increase the rotational moment that occurs at the movable scroll 3.

In the present embodiment, the fixed wrap 2 b is formed such that the center 2 d of the base circle 2 c is shifted from the center (not shown) of the fixed bottom plate 2 a. Also, the movable wrap 3 b is formed such that the center 3 d of the base circle 3 c is shifted from the center (not shown) of the movable bottom plate 3 a. This configuration makes it possible to reduce the outer diameter of the scroll unit 4, reduce the shell diameter of the scroll compressor 1, and reduce the size of the scroll compressor 1.

The fixed scroll 2 and the movable scroll 3 are disposed such that the fixed wrap 2 b is meshed with the movable wrap 3 b, a protruding end of the fixed wrap 2 b contacts the movable bottom plate 3 a, and a protruding end of the movable wrap 3 b contacts the fixed bottom plate 2 a. A chip seal is provided on each of the projecting end of the fixed wrap 2 b and the projecting end of the movable wrap 3 b.

Also, the fixed scroll 2 and the movable scroll 3 are disposed such that the wall surface of the fixed wrap 2 b and the wall surface of the movable wrap 3 b partially contact each other in a state in which the angles in the circumferential direction of the fixed wrap 2 b and the movable wrap 3 b are shifted from each other. With this configuration of the present embodiment, a crescent-shaped first compression chamber C1 is formed by an inner wall surface 3 b 1 of the movable wrap 3 b and an outer wall surface 2 b 2 of the fixed wrap 2 b, and a crescent-shaped second compression chamber C2 is formed by an inner wall surface 2 b 1 of the fixed wrap 2 b and an outer wall surface 3 b 2 of the movable wrap 3 b (see FIGS. 7 and 8 , described later).

The movable scroll 3 is attached such that the center (axial center) of the movable bottom plate 3 a is shifted from the center (axial center) of the fixed bottom plate 2 a and is caused by a drive mechanism to revolve around the center of the fixed bottom plate 2 a while being prevented from rotating by an anti-rotation mechanism 30, described later. The radius of the revolution may be determined by a contact between the fixed wrap 2 b and the movable wrap 3 b. As a result of the revolution, the first compression chamber C1 and the second compression chamber C2 move from the winding terminal end 3 f of the movable wrap 3 b and the winding terminal end 2 f of the fixed wrap 2 b toward the center, and the volume of the first compression chamber C1 and the volume of the second compression chamber C2 decrease. Accordingly, a fluid (for example, a refrigerant gas) taken into the first compression chamber C1 from the winding terminal end 3 f of the movable wrap 3 b is compressed, and a fluid (for example, a refrigerant gas) taken into the second compression chamber C2 from the winding terminal end 2 f of the fixed wrap 2 b is compressed.

As illustrated in FIGS. 3 and 4 , a recess 3 h is formed at a winding start end 3 g of the movable wrap 3 b. The recess 3 h is indented from the inner wall surface 3 b 1 of the winding start end 3 g of the movable wrap 3 b.

As illustrated in FIG. 1 , a housing of the scroll compressor 1 includes a center housing 6 that houses the scroll unit 4, a front housing 7 disposed in front of the center housing 6, and a rear housing 8 disposed behind the center housing 6.

In the present embodiment, the center housing 6 is formed as a housing (outer shell) for the scroll unit 4 and is integrally formed together with the fixed scroll 2. Alternatively, the fixed scroll 2 and the center housing 6 may be provided as separate components, and the fixed scroll 2 may be housed in and fixed to the center housing 6. The rear side of the center housing 6 is closed by the fixed bottom plate 2 a, and the front side of the center housing 6 is open.

The front housing 7 is fastened to the opening side of the center housing 6 with bolts (not shown). The front housing 7 supports the movable scroll 3 in a thrust direction and also houses a drive mechanism for the movable scroll 3.

Also, an intake chamber 9 for the fluid is formed inside of the front housing 7. The intake chamber 9 is connected to an intake port (not shown) formed in the outer wall of the front housing 7.

A bulging part 10 is formed in parts in the circumferential direction of the front housing 7 and the center housing 6. A fluid passage space 11 is formed inside of the bulging part 10, extends in a direction parallel to the compressor central axis, and guides the fluid from the intake chamber 9 in the front housing 7 to the vicinity of the winding terminal end 2 f of the fixed wrap 2 b of the scroll unit 4 in the center housing 6 and to the vicinity of the winding terminal end 3 f of the movable wrap 3 b.

The rear housing 8 is fastened, with bolts 12, to an end of the center housing 6 to face the fixed bottom plate 2 a such that a discharge chamber 13 for the fluid is formed between the rear housing 8 and the back surface of the fixed bottom plate 2 a. A discharge hole 14 for discharging a compressed fluid is formed in the center of the fixed bottom plate 2 a and a discharge valve 15, which is, for example, a one-way valve, is provided for the discharge hole 14. The discharge hole 14 is connected to the discharge chamber 13 via the discharge valve 15. The discharge chamber 13 is connected to a discharge port (not shown) that is formed in the outer wall of the rear housing 8.

The fluid is introduced from the intake port into the intake chamber 9 in the front housing 7, is taken into the first compression chamber C1 and the second compression chamber C2 from the outer periphery of the scroll unit 4 via the fluid passage space 11 inside of the bulging part 10 of the front housing 7 and the center housing 6, and is then compressed. The fluid compressed in the first compression chamber C1 and the fluid compressed in the second compression chamber C2 are combined and discharged from the discharge hole 14, which is formed in the center of the fixed bottom plate 2 a, into the discharge chamber 13 in the rear housing 8, and are discharged to the outside via the discharge port.

The front housing 7 includes a thrust receiver 17 that is disposed inside of an outer peripheral part fastened with bolts (not shown) to the opening side of the center housing 6 and faces the back surface of the movable bottom plate 3 a. The thrust receiver 17 receives a thrust force from the movable scroll 3 via a thrust plate 16.

Also, a central part of the front housing 7 rotatably supports a drive shaft 20 that constitutes the core of the drive mechanism for the movable scroll 3. One end of the drive shaft 20 protrudes from the front housing 7, and a pulley 22 is attached to the one end of the drive shaft 20 via an electromagnetic clutch 21. The drive shaft 20 is rotated by a rotational driving force that is input from the pulley 22 via the electromagnetic clutch 21. Another end of the drive shaft 20 is connected to the movable scroll 3 via a crank mechanism.

In the present embodiment, the crank mechanism includes a cylindrical boss 23 protruding from the back surface of the movable bottom plate 3 a and an eccentric bushing 25 eccentrically attached to a crank 24 provided at an end of the drive shaft 20. The eccentric bushing 25 is fit into the boss 23 via a bearing (e.g., a sliding bearing) 26. Also, a balance weight 27 is attached to the eccentric bushing 25 to counterbalance the centrifugal force generated when the movable scroll 3 is driven.

As illustrated in FIG. 6 , the anti-rotation mechanism 30 is constituted by multiple (five, in the present embodiment) rotation prevention parts 33 that are arranged at regular intervals along the circumferential direction near the outer edge of the back surface of the movable bottom plate 3 a. As illustrated in FIG. 5 , each of the rotation prevention parts 33 includes a ring 31 press-fit into a circular hole formed in the back surface (which faces the thrust receiver 17 of the front housing 7) of the movable bottom plate 3 a and a pin 32 that protrudes from the thrust receiver 17 of the front housing 7, passes through the thrust plate 16, and is loosely fit in the inside of the ring 31. Here, at least three rotation prevention parts 33 are necessary to prevent the movable scroll 3 from rotating, while enabling the movable scroll 3 to revolve around the axial center of the fixed scroll 2.

The operation of the scroll compressor 1 with the above configuration is described below with reference to FIGS. 7 through 13 . FIGS. 7 through 11 illustrate operating states of the scroll compressor 1. FIG. 12 is a graph showing the relationships between the pressures in the first compression chamber C1, the second compression chamber C2, and a final compression chamber C4 and a crank angle. FIG. 13 is a graph showing a relationship between a force (rotational moment) applied to the pin 32 and a crank angle. Here, a solid curve in FIG. 13 corresponds to the scroll compressor 1 of the present embodiment, and a dashed curve in FIG. 13 corresponds to a related-art scroll compressor. In the related-art scroll compressor, the involute angle θ1 is the same as the involute angle θ2, and the size (at least the length in a direction along the involute curve of the movable wrap 3 b) of the recess 3 h is smaller than the size of the recess 3 h in the present embodiment.

When the pulley 22 is rotated by a rotational driving force from the outside, the drive shaft 20 is rotated by the electromagnetic clutch 21, and the movable scroll 3 is caused by the crank mechanism to revolve around the axial center of the fixed scroll 2 while being prevented from rotating by the anti-rotation mechanism 30. As a result of the revolution of the movable scroll 3, the fluid (refrigerant gas) is taken into the first compression chamber C1 and the second compression chamber C2 between the fixed wrap 2 b and the movable wrap 3 b of the scroll unit 4 from the intake port and via the intake chamber 9 and the fluid passage space 11.

Here, in the present embodiment, the involute angle θ1 ending at the winding terminal end 2 f of the fixed wrap 2 b is less than the involute angle θ2 ending at the winding terminal end 3 f of the movable wrap 3 b. Accordingly, after the winding terminal end 3 f of the movable wrap 3 b contacts the outer wall surface 2 b 2 of the fixed wrap 2 b and the first compression chamber C1 is thereby closed, as illustrated in FIG. 7 , the winding terminal end 2 f of the fixed wrap 2 b contacts the outer wall surface 3 b 2 of the movable wrap 3 b and the second compression chamber C2 is thereby closed, as illustrated in FIG. 8 . With this configuration, because the first compression chamber C1 always compresses the fluid ahead of the second compression chamber C2, the pressure in the first compression chamber C1 is always higher than the pressure in the second compression chamber C2 (see crank angles of 0 to 360 degrees in FIG. 12 ). Hence, the rotational moment generated in the scroll compressor 1 becomes always greater than the rotational moment generated in the related-art scroll compressor (see FIG. 13 ). Here, the direction of the rotational moment corresponds to the direction of the revolution of the movable scroll 3.

As illustrated in FIGS. 9 and 10 , the fluid compressed as a result of the reduction in the volume of the first compression chamber C1 caused by the revolution of the movable scroll 3 combines with the fluid in a third compression chamber C3 located in the center through the recess 3 h of the movable wrap 3 b. That is, in or after the operating state illustrated in FIG. 9 , the first compression chamber C1 communicates with the third compression chamber C3 through the recess 3 h of the movable wrap 3 b. The third compression chamber C3 includes the discharge hole 14 and is surrounded by the fixed wrap 2 b and the movable wrap 3 b. In this operating state, the discharge valve 15 is closed, and the pressure in the third compression chamber C3 is higher than the pressure in the first compression chamber C1. Accordingly, in a period in which the operating state illustrated in FIG. 9 changes to the operating state illustrated in FIG. 10 , the high-pressure fluid in the third compression chamber C3 flows into (flows back into) the first compression chamber C1 through the recess 3 h of the movable wrap 3 b. As a result, the pressure in the first compression chamber C1 sharply increases (see crank angle α in FIGS. 12 and 13 ). In the present embodiment, the crank angle α is, for example, 310 degrees, but it is not limited thereto. As a result of the sharp increase of the pressure in the first compression chamber C1 at the crank angle α, the difference between the pressure in the first compression chamber C1 and the pressure in the second compression chamber C2 increases (see crank angles α to 360 degrees in FIG. 12 ). Accordingly, as shown in FIG. 13 , this configuration makes it possible to suppress reduced rotational moments at crank angles from a to 360 degrees compared to the related-art scroll compressor.

On the other hand, as illustrated in FIG. 10 and FIG. 11 , the fluid compressed as a result of the reduction in the volume of the second compression chamber C2 caused by the revolution of the movable scroll 3 combines with the fluid in the first compression chamber C1 that has been combined with the fluid in the third compression chamber C3. That is, immediately after the operating state illustrated in FIG. 10 , the first compression chamber C1, the second compression chamber C2, and the third compression chamber C3 are combined to form the final compression chamber C4, and as a result, the second compression chamber C2 communicates with the discharge hole 14. FIG. 12 shows that the fluid in the final compression chamber C4 is compressed and the pressure in the final compression chamber C4 increases at or after the crank angle of 360 degrees.

When the pressure in the final compression chamber C4 reaches a discharge pressure, the discharge valve 15 opens, and the fluid in the final compression chamber C4 is discharged through the discharge hole 14 into the discharge chamber 13.

As described above, in the scroll compressor 1 of the present embodiment, the center of the movable bottom plate 3 a is shifted from the center 3 d of the base circle 3 c of the movable wrap 3 b. With this configuration, a distance L (not shown) between the center of the compression reaction force applied to the movable scroll 3 and the center of the movable bottom plate 3 a varies during one revolution of the movable scroll 3. The center of the compression reaction force applied to the movable scroll 3 is at the midpoint between the center 2 d of the base circle 2 c and the center 3 d of the base circle 3 c when the pressure in the first compression chamber C1 is the same as the pressure in the second compression chamber C2. As the pressure in the first compression chamber C1 becomes higher than the pressure in the second compression chamber C2, the center of the compression reaction force moves further away from the center of the movable bottom plate 3 a (in other words, the distance L increases); and in the opposite case, the center of the compression reaction force moves closer to the center of the movable bottom plate 3 a (in other words, the distance L decreases). In the present embodiment, the distance L is smallest at around each of the crank angles of 0, 360, and 720 degrees shown in FIGS. 12 and 13 . Here, the rotational moment described above indicates a moment around the center of the movable bottom plate 3 a and is the product of the compression reaction force and the distance L. The compression reaction force varies during one revolution of the movable scroll 3 and is smallest at around, for example, each of the crank angles of 0, 360, and 720 degrees shown in FIGS. 12 and 13 . Thus, because the crank angle at which the distance L is smallest is close to the crank angle at which the compression reaction force is smallest, there is a concern that the rotational moment at that angle (at around a crank angle of 0, 360, or 720 degrees) may be reduced.

To address this concern, measures [1] and [2] below are adopted in the present embodiment.

[1] The involute angle θ1 ending at the winding terminal end 2 f of the fixed wrap 2 b is made less than the involute angle θ2 ending at the winding terminal end 3 f of the movable wrap 3 b. With this configuration, after the winding terminal end 3 f of the movable wrap 3 b contacts the outer wall surface 2 b 2 of the fixed wrap 2 b and the first compression chamber C1 is thereby closed, as illustrated in FIG. 7 , the winding terminal end 2 f of the fixed wrap 2 b contacts the outer wall surface 3 b 2 of the movable wrap 3 b and the second compression chamber C2 is thereby closed, as illustrated in FIG. 8 . That is, because the first compression chamber C1 always compresses the fluid ahead of the second compression chamber C2, the pressure in the first compression chamber C1 is always higher than the pressure in the second compression chamber C2 (see crank angles of 0 to 360 degrees in FIG. 12 ). This makes it possible to raise the level of the rotational moment to be generated (see FIG. 13 ).

[2] As illustrated in FIGS. 9 through 11 , after the first compression chamber C1 communicates with the third compression chamber C3 through the recess 3 h of the movable wrap 3 b, the second compression chamber C2 communicates with the discharge hole 14. For example, this makes it possible to increase the difference between the pressure in the first compression chamber C1 and the pressure in the second compression chamber C2 at crank angles between a and 360 degrees as shown in FIGS. 12 and 13 (see FIG. 12 ) and thereby makes it possible to suppress reduced rotational moments (see FIG. 13 ).

Adopting the measures [1] and [2] described above makes it possible to suppress reduced rotational moments and thereby makes it possible to cause the pin 32 to be always in contact with the inner surface of the ring 31. This in turn makes it possible to prevent the pin 32 from colliding with the ring 31 and thereby makes it possible to reduce the occurrence of vibration and noise in the anti-rotation mechanism 30.

According to the present embodiment, the scroll compressor 1 includes the fixed scroll 2 including the fixed bottom plate 2 a having the discharge hole 14 in the center of the fixed bottom plate 2 a and the spiral fixed wrap 2 b erected on the fixed bottom plate 2 a, the movable scroll 3 including the movable bottom plate 3 a and the spiral movable wrap 3 b that is erected on the movable bottom plate 3 a and is meshed with the fixed wrap 2 b, the first compression chamber C1 formed by the inner wall surface 3 b 1 of the movable wrap 3 b and the outer wall surface 2 b 2 of the fixed wrap 2 b, the second compression chamber C2 formed by the inner wall surface 2 b 1 of the fixed wrap 2 b and the outer wall surface 3 b 2 of the movable wrap 3 b, and the anti-rotation mechanism 30 that prevents the rotation of the movable scroll 3. The scroll compressor 1 is configured such that the movable scroll 3 is caused to revolve around the axial center of the fixed scroll 2 while the rotation of the movable scroll 3 is prevented by the anti-rotation mechanism 30 to change the volume of the first compression chamber C1 and the volume of the second compression chamber C2 and thereby cause the fluid in the first compression chamber C1 and the fluid in the second compression chamber C2 to be compressed separately and then discharged together through the discharge hole 14 into the discharge chamber 13. The fixed wrap 2 b may be formed according to an involute curve that is based on the base circle 2 c of the fixed wrap 2 b. The movable wrap 3 b may be formed according to an involute curve that is based on the base circle 3 c of the movable wrap 3 b. The involute angle θ1 from the reference point 2 e on the base circle 2 c of the fixed wrap 2 b to the winding terminal end 2 f of the fixed wrap 2 b is less than the involute angle θ2 from the reference point 3 e on the base circle 3 c of the movable wrap 3 b to the winding terminal end 3 f of the movable wrap 3 b. With this configuration, after the winding terminal end 3 f of the movable wrap 3 b contacts the outer wall surface 2 b 2 of the fixed wrap 2 b and the first compression chamber C1 is thereby closed, the winding terminal end 2 f of the fixed wrap 2 b contacts the outer wall surface 3 b 2 of the movable wrap 3 b and the second compression chamber C2 is thereby closed. Accordingly, the pressure in the first compression chamber C1 becomes constantly higher than the pressure in the second compression chamber C2. This makes it possible to constantly generate a rotational moment in the movable scroll 3 and thereby makes it possible to suppress reduced rotational moments.

According to the present embodiment, the movable wrap 3 b includes the recess 3 h that is formed at the winding start end 3 g of the movable wrap 3 b and is indented from the inner wall surface 3 b 1 of the winding start end 3 g. The scroll compressor 1 further includes the third compression chamber C3 that includes the discharge hole 14 and is surrounded by the fixed wrap 2 b and the movable wrap 3 b. After the first compression chamber C1 communicates with the third compression chamber C3 through the recess 3 h of the movable wrap 3 b, the second compression chamber C2 communicates with the discharge hole 14. This makes it possible to increase the difference between the pressure in the first compression chamber C1 and the pressure in the second compression chamber C2 and thereby makes it possible to suppress reduced rotational moments.

Also, according to the present embodiment, the anti-rotation mechanism 30 includes the ring 31 that is press-fit into the circular hole formed in one of the back surface of the movable bottom plate 3 a and the housing wall facing the back surface and the pin 32 that protrudes from another one of the back surface and the housing wall and is loosely fit in the inside of the ring 31. In such a configuration of the anti-rotation mechanism 30, it possible to reduce the occurrence of vibration and noise in the anti-rotation mechanism 30.

According to the present embodiment, the center of the fixed bottom plate 2 a is shifted from the center 2 d of the base circle 2 c of the fixed wrap 2 b. Also, the center of the movable bottom plate 3 a is shifted from the center 3 d of the base circle 3 c of the movable wrap 3 b. In such a configuration of the scroll compressor 1, it possible to reduce the occurrence of vibration and noise in the anti-rotation mechanism 30.

An external drive source for driving the scroll compressor 1 of the present embodiment may be, for example, a vehicle engine or a motor. Also, the scroll compressor 1 may include, as an integral component, a motor that serves as the drive source.

For example, the scroll compressor 1 of the present embodiment may be incorporated into a refrigerant circuit of a vehicle air conditioner and configured to compress and discharge a refrigerant that is taken in from the low pressure side of the refrigerant circuit.

The scroll unit 4 (the fixed scroll 2 and the movable scroll 3) described above may also be used for a scroll expander. For example, the scroll expander may be incorporated into a refrigerant circuit of a Rankine cycle device for a vehicle and configured to expand a refrigerant introduced from the refrigerant circuit to generate power (or recover power from the refrigerant).

A preferred embodiment of the present invention is described above. However, the present invention is not limited to the above-described embodiment and, clearly, the embodiment may be further modified based on the technical idea of the present invention.

REFERENCE SYMBOL LIST

1 . . . scroll compressor, 2 . . . fixed scroll, 2 a . . . fixed bottom plate, 2 b . . . fixed wrap, 2 b 1 . . . inner wall surface, 2 b 2 . . . outer wall surface, 2 c . . . base circle, 2 d . . . center, 2 e . . . reference point, 2 f . . . winding terminal end, 3 . . . movable scroll, 3 a . . . movable bottom plate, 3 b . . . movable wrap, 3 b 1 . . . inner wall surface, 3 b 2 . . . outer wall surface, 3 c . . . base circle, 3 d . . . center, 3 e . . . reference point, 3 f . . . winding terminal end, 3 g . . . winding start end, 3 h . . . recess, 4 . . . scroll unit, 6 . . . center housing, 7 . . . front housing, 8 . . . rear housing, 9 . . . intake chamber, 10 . . . bulging part, 11 . . . fluid passage space, 13 . . . discharge chamber, 14 . . . discharge hole, 15 . . . discharge valve, 20 . . . drive shaft, 30 . . . anti-rotation mechanism, 31 . . . ring, 32 . . . pin, 33 . . . rotation prevention part, C1 . . . first compression chamber, C2 . . . second compression chamber, C3 . . . third compression chamber, C4 . . . final compression chamber, θ1, θ2 . . . involute angle 

1. A scroll compressor comprising: a fixed scroll including a fixed bottom plate having a discharge hole in a center of the fixed bottom plate and a spiral fixed wrap erected on the fixed bottom plate; a movable scroll including a movable bottom plate and a spiral movable wrap that is erected on the movable bottom plate and is meshed with the fixed wrap; a first compression chamber formed by an inner wall surface of the movable wrap and an outer wall surface of the fixed wrap; a second compression chamber formed by an inner wall surface of the fixed wrap and an outer wall surface of the movable wrap; and an anti-rotation mechanism that prevents rotation of the movable scroll, wherein the scroll compressor is configured such that the movable scroll is caused to revolve around an axial center of the fixed scroll while the rotation of the movable scroll is prevented by the anti-rotation mechanism to change a volume of the first compression chamber and a volume of the second compression chamber and thereby cause a fluid in the first compression chamber and a fluid in the second compression chamber to be compressed separately and then discharged together through the discharge hole into a discharge chamber; and an involute angle from a reference point on a base circle of the fixed wrap to a winding terminal end of the fixed wrap is less than an involute angle from a reference point on a base circle of the movable wrap to a winding terminal end of the movable wrap.
 2. The scroll compressor as claimed in claim 1, wherein after the winding terminal end of the movable wrap contacts the outer wall surface of the fixed wrap and the first compression chamber is thereby closed, the winding terminal end of the fixed wrap contacts the outer wall surface of the movable wrap and the second compression chamber is thereby closed.
 3. A scroll compressor comprising: a fixed scroll including a fixed bottom plate having a discharge hole in a center of the fixed bottom plate and a spiral fixed wrap erected on the fixed bottom plate; a movable scroll including a movable bottom plate and a spiral movable wrap that is erected on the movable bottom plate and is meshed with the fixed wrap; a first compression chamber formed by an inner wall surface of the movable wrap and an outer wall surface of the fixed wrap; a second compression chamber formed by an inner wall surface of the fixed wrap and an outer wall surface of the movable wrap; and an anti-rotation mechanism that prevents rotation of the movable scroll, wherein the scroll compressor is configured such that the movable scroll is caused to revolve around an axial center of the fixed scroll while the rotation of the movable scroll is prevented by the anti-rotation mechanism to change a volume of the first compression chamber and a volume of the second compression chamber and thereby cause a fluid in the first compression chamber and a fluid in the second compression chamber to be compressed separately and then discharged together through the discharge hole into a discharge chamber; and after a winding terminal end of the movable wrap contacts the outer wall surface of the fixed wrap and the first compression chamber is thereby closed, a winding terminal end of the fixed wrap contacts the outer wall surface of the movable wrap and the second compression chamber is thereby closed.
 4. The scroll compressor as claimed in claim 1, wherein the movable wrap includes a recess that is formed at a winding start end of the movable wrap and is indented from an inner wall surface of the winding start end.
 5. The scroll compressor as claimed in claim 4, further comprising: a third compression chamber that includes the discharge hole and is surrounded by the fixed wrap and the movable wrap, wherein the second compression chamber communicates with the discharge hole after the first compression chamber communicates with the third compression chamber through the recess.
 6. The scroll compressor as claimed in claim 1, wherein the anti-rotation mechanism includes a ring that is press-fit into a circular hole formed in one of a back surface of the movable bottom plate and a housing wall facing the back surface, and a pin that protrudes from another one of the back surface and the housing wall and is loosely fit in an inside of the ring.
 7. The scroll compressor as claimed in claim 1, wherein a center of the fixed bottom plate is shifted from a center of the base circle of the fixed wrap; and a center of the movable bottom plate is shifted from a center of the base circle of the movable wrap. 